#pragma once
#include<string>
#include<iostream>

class Timestamp{
    public:
        Timestamp();
        explicit  Timestamp(int64_t microSecondsSinceEpoch);
        static Timestamp now();
        // const修饰 不能修改成员变量
        std::string toString() const;

    private:
        int64_t microSecondsSinceEpoch_;
};